A liquid crystal display device can use spherical or cylindrical silica or plastic beads to maintain a constant interval between upper and lower panels. Since the beads are randomly applied to and distributed on a glass substrate, they may be located within active pixels. In this case, the contrast ratio of the liquid crystal display device is lowered due to decreased opening ratio of the liquid crystal display device and light leakage (a phenomenon in which light is emitted in directions other than the forward direction).
To solve these problems, spacers have been formed by photolithography. According to this method, a photosensitive resin composition is applied to a glass substrate, and the photosensitive resin composition is irradiated with UV light through a patterned mask. The exposed portions of the photosensitive resin composition are developed to form spacers according to the pattern of the mask on desired areas of the glass substrate other than within active pixels. However, the spacers have poor processing stability, low compressive displacement and low recovery rate. Thus a layer underlying R, G and B pixels of a color filter of a liquid crystal display device can be abnormally deformed to form gap defects between or within the respective pixels. This problem leads to color or contrast defects, which can deteriorate the quality of images.
Various attempts have been made to solve the above problems. For example, Korean Patent Registration No. 10-0268697 teaches a use of a copolymer comprising a conjugated unsaturated diolefinic compound as a binder resin to achieve high strength and recovery rate.
However, synthesis of copolymers including 1,3-butadiene as a structural unit, which is mainly used to achieve increased elastic recovery, requires the use of a high-pressure reactor and it can be difficult to control the content of 1,3-butadiene due to its low reactivity. Thus, there is an increasing demand to develop a binder that exhibits characteristics comparable to copolymers using 1,3-butadiene and can be easily synthesized.
On the other hand, recent trends towards the use of large substrates have brought about an increase in exposure time during the formation of column spacers using photo-curable resist compositions, resulting in a reduction in productivity. In view of the foregoing, there is a need in the art to develop a resist composition for column spacers for a liquid crystal display device with a high productivity.